The present invention relates to a rocker arm having a valve guide to insure and operative connection between the valve guide and a valve pad of the valve guide, and more specifically, to a spring clip valve guide that permits relaxed manufacturing tolerances.
In automotive internal combustion piston engines of the overhead camshaft type, it is known to provide a rocker arm assembly that cooperates with a lash adjuster having a cylindrical plunger and a finger follower that is pivotable about a pivot point during engine operation. To insure proper engagement between a lash adjuster and rocker arm assembly, it is known to provide a double walled end section formed by integral parallel straps that are bent 180xc2x0 parallel to and in contact with a lower wall and welded thereto to provide two lateral seating surfaces. However, doubled walled end sections are disadvantageous because the double walled section results in a larger mass and consequently a greater amount of inertia for the lever. Moreover, additional manufacturing steps and increased production costs are required to fold and weld the straps to insure proper formation of the double walled sections.
It has also been known to provide a groove around a plunger for a lash adjuster to receive edges of a side-ways U-shaped retainer clip. A top portion of the side-ways U-shaped retainer clip engages an upwardly deformed rounded raised portion of the rocker arm with one arm curving around the upwardly deformed rounded raised portion. Another arm extends below a bottom surface of the rocker arm and engages the groove of the lash adjuster once the plunger is received in the upwardly deformed rounded raised portion of the rocker arm. However, while reducing weight, such arrangements are undesirable because the reduced diameter at the groove reduces the bending stiffness and strength of the plunger of the lash adjuster. Additional manufacturing costs are incurred for forming the upwardly deformed rounded raised portion. Moreover, tight tolerances must be maintained to insure that the spring clip properly engages both the lash adjuster and the upwardly deformed rounded raised portion.
Accordingly, there exists a need for a simplified construction for maintaining proper engagement between a lash adjuster and a rocker arm assembly that allows for an improved valve pad surface, relaxed tolerances for the valve tip and reduced reciprocating mass over the valve.
The present invention is directed to a rocker arm assembly pivotably mounted about a central roller that includes a main body section and first and second ends. In accordance with one aspect of the invention, the first end includes a detent into which a lash adjuster extending from the bore of the cylinder head is slidingly received. The second end includes apertures into which a distal end of a wire spring clip may be retainingly engaged. A cross member of the wire clip engages an outwardly extending land portion in a snap-fit relationship. When engaged, the wire spring clip forms two downwardly extending parallel arms that are spaced away from the bottom surface of the rocker arm. In accordance with the invention, a valve stem from a valve member may be positioned between the downwardly extending arms.
The wire spring clip advantageously provides additional contact points for consistent contact between the rocker arm assembly and the valve stem. The consistent contact allows for reduced machine tolerances of both the contact portion of the rocker arm and the valve stem tip during manufacture without sacrificing performance. Additionally, the consistent contact also provides an improved valve pad surface by allowing a smaller chamfer on the valve tip. Moreover, because the wire clip is relatively lightweight, reduced reciprocating mass over the valve is also achieved.